All nine members of slain family in California were shot

All nine family members found dead in a California home at the weekend were shot, the coroner's office has said.

Investigators were still working to determine how the victims were related.

The bodies of a 24-year-old woman and eight children ranging in age from one to 17 were found tangled in a pile of clothes when police went to the home about a child custody dispute on Friday.

Marcus Wesson, thought to be the father and grandfather of the victims, walked out of the home covered in blood and was booked on suspicion of nine counts of murder.

Police said Wesson, 57, may have been involved in polygamy and was thought to have fathered children with at least four women, including two of his own daughters.

Police said Wesson has co-operated with the investigation, but no motive had been determined.

Wesson's arraignment was scheduled for today with bail set at $US9 million ($A12 million).

Authorities expected to release the names of the victims soon.

Coroner Loralee Cervantes told the <i>Fresno Bee</i> newspaper that police conducted tests to determine if there was gunshot residue on the hands of one of the victims, indicating Wesson may have had help with the shootings.

The victims, who had six different mothers, showed no signs of physical or sexual abuse, the coroner said.

Acquaintances said Wesson and his family appeared to live a nomadic, insular existence. The family moved several times in recent years, from a small boat anchored off Santa Cruz to the mountains outside Watsonville, before settling in Fresno.

In the early 1990s, Wesson lived with a few children on a battered, eight-metre sailboat that had no toilet or bathing facilities.

During that time, he was jailed briefly after being convicted of welfare fraud, the <i>Santa Cruz Sentinel</i> reported.

Wesson failed to list his boat as an asset on welfare forms. He also was frequently delinquent with his slip fees, the newspaper said.

Other acquaintances said Wesson appeared with women and children who seemed to be under his control.

Frank Muna, a lawyer who once sold the murder suspect a house, said the women wore dark robes and scarves, walked behind Wesson and did not speak when he was present.

Mr Muna said police interviewing him said Wesson killed his children because he didn't want them taken away from him.

The children were home-schooled because Wesson did not trust public education, his sons said, and Wesson, who did not work, was supported by the women.

Police Chief Jerry Dyer said investigators would need DNA testing to determine the biological parents of all the victims.

"We're in the very early stages of a very complex investigation," he said.

Wesson's sons, Dorian, 29, who lives in Santa Cruz, and Serafino, 19, who lived at the California house, could not say whether he was married or how many children he had fathered, the <i>Fresno Bee</i> reported.

They said the family belonged to the Seventh-day Adventist church.

But a church spokeswoman said there was no record of Wesson's membership.